高压物理学报

Dependence of the Quenching Pressures of Ruby R-Line Fluorescence on the Wavelengths of the Incident Laser Beams under Ultra-High Pressure

LIU Zhen-Xian, CUI Qi-Liang, ZOU Guang-Tian

1991, 5(1): 1-7 . doi: 10.11858/gywlxb.1991.01.001

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Abstract:
The fluorescent spectra of ruby were measured by using solid argon and a 4∶1 methanol-ethanol mixture as pressure-transmitting media, respectively. Experimental results show that under ultra-high pressure the quenching pressures of ruby R-line fluorescence depend not only on the wavelengths of the incident laser beams, but also the degree of hydrostaticity in the chamber as well. The quenching pressure decreases with increasing wavelength and increases with decreasing degree of hydrostaticity. This phenomenon can be explained from the fact that the U and Y bands in the absorption spectrum of ruby shifts with increasing pressure.

High Order Elastic Constants and Equation of State for Isotropic and Cubic Symmetry Materials

WANG Ji-Fang

1991, 5(1): 8-12 . doi: 10.11858/gywlxb.1991.01.002

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Abstract:
We propose an equation of state expressed by combined SOEC, TOEC and FOEC. Those combined elastic constants are determined from the ultrasonic velocities under high pressure.

Crystallization of Pd40Ni40P20 Bulk Metallic Glass under High Pressure

XU Ying-Fan, HUANG Xin-Ming, CHEN Hong, WANG Wen-Kui

1991, 5(1): 13-19 . doi: 10.11858/gywlxb.1991.01.003

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Abstract:
The crystallization of bulk metallic glass of Pd40Ni40P20 was investigated under 4 GPa high pressure and atmosphere. The time-temperature transition curves were obtained. The results showed that the crystallization temperature of the glass increases with pressure at the rate of 15 K/GPa. The long-range diffusion-controlled growth and the viscous flow of the phase-separated melt were suppressed by the pressure. As high pressure annealing temperature close to the melting temperature, a new single phase of supersaturated solid solution was obtained, for which the lattice constant is 0.369 nm.

Effects of High Pressure Treatment on the Superconductivity of BiSrCaCu2Oy

CUI De-Liang, LIU Hong-Jian, WANG Yi-Feng, LI Li-Ping, SU Wen-Hui

1991, 5(1): 20-26 . doi: 10.11858/gywlxb.1991.01.004

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Abstract:
Based on the convention preparation of high Tc super conductor BiSrCaCu2Oy, the effects of heat-pressure and cool-pressure on the formation, structure and superconductivity of this sample have been studied. The results show that high pressure can make the synthesis time shorter and the synthesis temperature lower, but at the same time it may restrain the formation of the phase with larger lattice parameters (high Tc phase) and increase the content of impurity phase with smaller lattice parameters. For getting better superconductivity, the 1.5 PGa is a good pressure condition.

Dynamic Properties of LY-12 Aluminium Alloy under High Temperature Condensed StateHigh Temperature Elastic Modulus Measurements

WANG Chun-Kui, LIU Xiao-Ping

1991, 5(1): 27-34 . doi: 10.11858/gywlxb.1991.01.005

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Abstract:
Dynamic properties of metal materials at high temperatures are quite important in material sciences. This paper describes the elastic modulus measurements of LY-12 aluminium under dynamic loadings and at temperatures up to 450 ℃ by using one dimensional split Hopkinson bar and tubular furnace. With the observed elastic wave velocities c(T) of LY-12 Al at different temperatures, and based on the one dimensional theory of elastic stress wave propagation, the temperature dependence of Young's Models, E(T), of LY-12 Al can be obtained via c(T)=E(T)/T.

Properties of High-Tc Superconductors under High Pressure and Low Temperature

HAN Cui-Ying

1991, 5(1): 35-45 . doi: 10.11858/gywlxb.1991.01.006

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Abstract:
The pressure dependence of the superconducting transition temperatures Tc, of single crystal YBa2Cu3O7- (=0.46) and Bi2Sr2CaCu2Ox were measured. The pressure derivatives, dTc/dp, were determined to be 4.9 KGPa-1 for YBa2Cu3O7- (=0.46) and -0.4 KGPa-1 for Bi2Sr2CaCu2Ox. Such a large change in Tc with increasing pressure was never observed before in Y123 specimens with a Tc0 of about 47 K at p=0. The dTc/dp is a function of Tc0, which can be written as dTc/dp=b-mTc0 (b and m are constants). The results are explained via the pressure induced structure phase transition in Y123, the influence of the oxygen vacancies on the Tc.

Pressure Effects on FT-IR Spectrum of Stearic Acid

TANG Da-Xin, ZHANG Tie-Chen, WANG Hui, DONG Xi-Juan, ZOU Guang-Tian

1991, 5(1): 46-51 . doi: 10.11858/gywlxb.1991.01.007

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Abstract:
The effects of pre-pressure in the range 0~4 GPa on the correlation field splitting and solid state-melt state phase transition of the stearic acid were studied. By observing the change in the spectra intensities and frequencies of CH2 rocking mode and its correlation field component 'CH2, drastic effects of pre-pressure on correlation field splitting and molecular orientation in the crystal were observed. Although effect of pre-pressure on melting point of stearic acid has not been observed, a harden phenomenon of the 'CH2 mode was obtained. From this mechanism of temperature-induced phase transition was discussed

Long-Time Correlation Effects and Fractal Braonian Motion

WANG Ke-Gang, LONG Qi-Wei

1991, 5(1): 52-56 . doi: 10.11858/gywlxb.1991.01.008

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Abstract:
We present a comprehensive study of the motion of a damped Brownian particle undergoing a randomly fluctuating force with zero mean and a correlation function of a power-law time dependence, or C(t)~t-, 01, 12, instead of the Dirac delta-function. It is evident that this motion is fractional Brownian motion or fractal Brownian motion (fBm). The effective Fokker-Planck equation for fBm and its solution for fBm are presented. We have also established the quantitative relation of long-time correlation of power law time dependence to the fBm and anomalous diffusion.

Ultrasonic Equation of State for Isotropic Polycrystalline Al, Cu and Ta

ZHANG Shu-Hua

1991, 5(1): 57-61 . doi: 10.11858/gywlxb.1991.01.009

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Abstract:
By use of the ultrasonic pulse echo overlap technique, the elastic moduli of isotropic polycrystalline Al, Cu and Ta, and their pressure derivatives have been determined. The isotherms for these metals, calculated from Birch-Murnaghan equation of state are also compared with the shock wave isotherms.

A New Method for Calculating the Equation of State from Shock Compression DataOptimization of Grneisen Coefficient

LIN Hua-Ling, ZHANG Ruo-Qi

1991, 5(1): 62-70 . doi: 10.11858/gywlxb.1991.01.010

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Abstract:
In this paper, a new method for calculating the parameters in the Mie-Grneisen equation of state from shock compression data is presented. This method gives the best fit of the Grneisen coefficients calculated along the experimental shock adiabatic with the results from the vibration theory of crystal lattices. The results of 0K, Q, q and Grneisen coefficients for twenty-three materials are shown. The average relative derivation between the shock adiabatic calculated with these parameters and the experiments is within 1%.

Equation of State Calculations for Hot Dense U92

XUE Fu-Zeng, PAN Shou-Fu

1991, 5(1): 71-77 . doi: 10.11858/gywlxb.1991.01.011

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Abstract:
Within the approximations of spherical lattice cell, central-field and relativistic Fermi statistics, an average atom model is presented to calculated the electronic energy levels and equation of state for hot and dense U92. Zink's analytic potential is chosen as starting potential to solve Dirac-Slater equation satisfying the Weifnei-Seitz boundary condition. The electronic energy bands are not taken into account. The pressure ionization effects are included by level degeneracy as a continuous function of matter densities of U92.

1991 Vol. 5, No. 1

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